Brass plated carbon fiber reinforced rubber

ABSTRACT

Reinforced elastomeric compositions comprising brass plated fibers comprising a core material of carbon, glass, polymer or metal covered with a layer of brass incorporated into an elastomeric material.

[0001] This application claims the priority of Provisional Application Serial No. 60/231,291 filed Sep. 8, 2000.

[0002] The present invention relates to elastomeric materials reinforced with metal plated fibers. Specifically, the present invention is directed to rubber compositions strengthened by brass plated carbon fibers, and methods of making the same. The present invention is also directed to methods of using such strengthened compositions in articles that require superior mechanical properties, as well as flexibility characteristics.

[0003] The phrase “elastomeric material” or “elastomer” as used herein is intended to mean natural or synthetic rubber, polymers or copolymers. Elastomers include vulcanized or unvulcanized natural or synthetic rubber, as well as any well-known organic polymer or copolymer, such as the flexible and resilient forms of nylons, other polyamides, polyesters, styrenes, vinyls, aramids, and fluoropolymers. Presently, elastomer materials are reinforced with steel, polyester, nylon, Kevlar®, Nomex® and the like. Products in which these reinforced elastomers have been used include the automotive industry. Such products include, for example, steel radial tires, belts and hoses. However, reinforced elastomers can be used in other applications that require strength and flexibility, such as bullet resistant structures and cordage products, precision timing belts and conveyor belts.

[0004] The effectiveness, and thus end-use of the reinforced elastomer is known to be a function of the reinforcing material. For example, while elastomeric material can be reinforced with steel, applications that require durability at high speed, such as in airplane and motorcycle tires, have been limited by the deformability and flexibility properties required in such applications. Thus, conventional airplane and motorcycle tires are reinforced with nylon or other synthetic cord rather than steel.

[0005] In addition, belt applications, namely timing or conveyor belts, have to exhibit a combination of flexibility and strength. Advantageously, a reinforced material used in belt applications must also be able to dissipate heat generated at increased operating temperature more effectively than products traditionally used in such applications. More advantageously, a reinforced material used in belt applications would not only be able to dissipate heat effectively, but would have a tailorable coefficient of thermal expansion. As used herein, “tailorable coefficient of thermal expansion” means a thermal expansion that could be altered, within a finite range, from a negative value to zero to a desired positive value, depending on the processing conditions of the plated fiber. This property would allow the resulting reinforced product to exhibit thermal stability.

[0006] Thermal stability is important in applications that expose the reinforced material to temperatures that may adversely affect the resulting product. For example, in high precision belt applications, even a small increase in slack due to thermal expansion associated with traditional metal filler would be unwanted. Similarly, in tire applications an increase in thermal expansion during use may change the profile, and thus the wear of the tire.

[0007] Still further, it is important that the reinforced material have high tensile strengths, great resistance to elongation and high energy absorption properties.

[0008] It would be desirable to provide a reinforced elastomeric material that exhibits the improved mechanical, thermal and other properties mentioned above, but which can be processed using known techniques.

[0009] To solve the foregoing problems associated with the prior art, the present invention utilizes metal plated fibers to reinforce elastomeric materials. This new reinforced material preferably comprises brass plated carbon fibers that are incorporated into rubber. Products comprising rubber reinforced with brass plated carbon fiber have improved tensile and elongation properties over present elastomers reinforced with either steel, Kevlar or Nomex, and are able to dissipate heat better than traditional steel, Kevlar or Nomex reinforced materials. In addition, products made in accordance with the present invention have a tailorable coefficient of thermal expansion, and thus are thermally stable at increased operating temperatures.

[0010] Accordingly, a subject of the present invention is a reinforced elastomeric composition comprising brass plated fibers, wherein the fibers are selected from the group consisting of carbon, glass, polymer, and metal. Depending on the orientation of the fiber, the application of the resulting product differs. For example, a product having the fibers oriented perpendicular to an outer surface is able to dissipate heat away from the outer surface more effectively than fibers oriented in a random or parallel fashion, and thus can be used as a heat sink. However, a product comprising fibers oriented parallel to an outer surface may exhibit improved mechanical properties that may make it more attractive as a hose, belt or tire.

[0011] In addition, through processing conditions, the composition is able to have a coefficient of thermal expansion that can be tailored to specific applications. For example, some belt or tire applications may require precision engineering, and thus benefit from a coefficient of thermal expansion that is negative or zero across the operating temperature region. Tailoring the coefficient of thermal expansion would be a function of the method of depositing the brass, i.e., if it applied to the fiber by electroplating, electroless plating or chemical vapor deposition, as well as the amount of brass and fiber incorporated into the elastomeric material.

[0012] In another aspect, the invention provides a method of producing a composition in which the metal plated fiber is treated with a sizing agent, preferably latex-based, to enhance adhesion to the elastomeric material. This aspect is primarily used when the elastomeric material is a rubber.

[0013] The metal plated fiber of the present invention comprises a core material of carbon, glass, polymer or metal, which is covered with a metal layer formed of material selected from the group consisting of electroplated metal, chemical vapor deposited metal, and electroless plated metal. The method of coating and the use of such metal coated fibers are described in U.S. Pat. Nos. 4,680,093, 4,609,449 and 4,661,403, the entire contents of which are incorporated by reference herein. Preferably, the core material comprises aramid, fiberglass, graphite, stainless steel. Preferably the metal plated onto the fiber is brass.

[0014] By using the metal plated fibers described above, a reinforced product comprising a composition made in accordance with the present invention exhibits flexibility and elongation at break that are comparable to traditional steel or Kevlar reinforced elastomers, but which have tensile, thermal, resistance to elongation and high energy absorption properties much better than these traditional reinforced elastomers.

[0015] The present invention has been disclosed generally and by reference to embodiments thereof the scope of the invention is not limited to the disclosed embodiments but is defined by the appended claims and their equivalents. 

What is claimed is:
 1. Brass plated fibers comprising a core material of carbon, glass, polymer or metal which is covered with a layer of brass.
 2. A reinforced elastomeric composition comprising rubber or elastomeric material reinforced with the brass plated fibers according to claim
 1. 3. The composition of claim 2, wherein the fibers are selected from the group consisting of carbon, glass, polymer, and metal.
 4. A product formed from the composition of claim 1, wherein the product has at least one outer surface and said fibers are oriented perpendicular to said outer surface.
 5. The product of claim 4, wherein the product is a heat sink.
 6. The composition of claim 2 having a tailorable coefficient of thermal expansion.
 7. The composition of claim 6, wherein the coefficient of thermal expansion is negative or zero.
 8. A product formed from the composition of claim 2, wherein said product is a belt, hose or a tire.
 9. The composition of claim 2, wherein the brass is applied to said fiber by lectroplating, electroless plating or chemical vapor deposition.
 10. The article of claim 2, wherein the metal plated fibers comprise a coating formed of a sizing agent applied before the metal plated fibers are incorporated into the elastomeric material.
 11. The composition of claim 2, wherein the elastomer comprises vulcanized or unvulcanized natural rubber, nylon, polyester, styrene, vinyl, fluoropolymer and synthetic rubbers. 